Range computer



June 22, 1948. c, A LOVELL ETAL 2,443,624

RANGE COMPUTER 2 Sheets-Sheet 1 Filed April 25, 1942 32 vaL TA 65 $0URCEI Am GIVE T/c CLUTCHES to/vmoz.

CIRCUIT -c. A. LOVELL ;f" 0. B. PARK/NSON ATTORNE VOLTAGE 4- SOURCECONTROL CIRCUIT June 22, 1948- c. A. LOVELL ETAL 2,443,624

RANGE COMPUTER Filed April 23, 1942 t 2 Sheets-Sheet 2 FIG. 4

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lllll Ivy" OUTPUT cqA. LOVELL INVENTORSQ ,3 PARK/NSON AT7URNEY PatentedJune 22, 1 948 2,443,624 RANGE COMPUTER Clarence A. Lovell and David B.Parkinson,

Maplewood, N. J., assignors to Bell Telephone Laboratories,Incorporated, New York, N. Y., a

corporation of New York Application April 23, 1942, Serial No. 440,167

2 Claims. (Cl. 235-615) This invention relates to systems for the control of artillery fire, and particularly to systems for determining thedistance from an observa tion point to a target.

The object of the invention is'the determination of the distance from anobservation point to a target, and the representation of this distancein the form of an electrical difference of potential.

A feature of the invention is a method of determining the desireddistance by electromechanical means which attain a null balance.

I base line to the target, in the plane ABT. The

Another feature of the invention is a methodof representing the desireddistance inthe form of an electrical difference of potential obtained bymeasurements takenfrom two spaced points of observation and involvingonly the sine or cosine functions of the angles involved.

In one known system of this type, the -distance is determined by amethod involving the L difference of two tangent functions, and isrepresented by a voltage which is the direct algebraic sum of twovoltages. As the tangent functions vary from zero to infinity, it is notphysically possible to produce a representation of these functions forall angles. In the present invention, using only sine or cosinefunctions which vary from zero to unity, all values of these functionsmay be represented .by practical values of physical quantities. And, inthe known system, the desired quantity is represented by the algebraicsum of two voltages which are directly dependent upon the value of thevoltage of the source, thus any variation in the value of the .voltagefrom the source will directly affect the accuracy. In the presentinvention, a null method is used to determinethe desired voltage andthis voltage is thus not directly affected by changes in the voltagefrom the source.

In another known system, the desired distance is determined by a methodinvolving the cosecant function of an angle, and by the direct additionof voltages representing the logarithmicvalues of certain quantities. Inthis known system, also, the cosecant function cannot be represented forall angles by any physical means. and the accuracy of the determinationdepends upon the constancy of the source of voltage.

In the drawings,

Fig. l diagrammatically shows the observation points and the target;

' Tracking telescopes, or other suitable sighting devices, are locatedat the observation points A;-

B, Fig. 1, located at the extremities of a line AB having a known lengthm units. The tracking telescopes measure the angles a and ,6, from thetracking telescopes are mounted in some simple form of equatorialmounting with one axis of j rotation in the line AB. As shown in' Fig.2, the

axis of rotation H of thetracking telescope l2 may be pierced by a holel3, which may house suitable lenses, or, if preferred, a separatetelescope, or sighting points, may :be arranged paral lel to the axis ofrotation II. By sighting along the axis of rotation of one trackingtelescope to the axis of the other telescope, the axis of the firsttelescope may be moved into coincidence with the line AB and thetelescope is aligned to rotate in azimuth in a plane containing the lineAB.

The windings of the potentiometers I, 2, 4, Fig. 3, have a uniformresistance per unit length and extend over an effective are of 180degrees. The

wipers l4, l5 of the potentiometers l, 2 are respectively movedproportionally to the angles a and 8 described by the movements of thetracking telescopes at points A and B. The potentiometers I, 2 may, ifdesired, be mounted in the pedestals supporting the telescopes as shownin Fig. 2 and the wipers I 4, l5 may be moved directly, or throughsuitable gearing, by the telescopes.

A source of voltage l6, such as a battery, is connected to the windingsof the potentiometers I, 2. If the stations A, B are some distanceapart,

separate sources may be used. A source of voltage I! is connected to thewinding of the potentiometer 4. Preferably, the sources IE and H are soconnected that any changes in voltage occur simultaneously and to thesame degree in both sources.

The device I8 is any type of reversible power system which maybecontrolled in position and Fig. 2 shows a simple form of trackingtelescope;

Fig. 3 schematically shows a computing unit embodying the invention;

Fig. 4 schematically shows a system embodying the invention which iscontrolled by 'a single source of voltage; and

Fig. 5 schematically shows a repeater used in the system of Fig. 4.

movement by the variations in amplitude of an electric current. Forconvenience of description, but not as any limitation on the scope ofthe present invention, a device of the type'shown in- United StatesPatent 2,003,913, June 4, 1935, E. C. Wente, may be used. In this devicethe motor l9 drives the gear 20, meshing with the gears 2|, 22 looselymounted on the shaft 23. When a voltage is applied to the controlcircuit 24. one or the other of the magnetic clutches 25,

26, aifixed to the shaft 23, is energized to cause.

are connected to one of the wires 21, 3|, the source 39 is connected tothe other wire, the biasing voltage of the source 39 is reduced from thecut-off value to a normal value, and the resistance 34 is adjusted forthe change in impedance of the vacuum tubes 31, 38. Any other suitabletype of servo-motor may be used.

The clutches 25; 26 are controlled by the difference of potentialsupplied by the wires 21, 3| to the control circuit 24. The source I6 isconnected across the winding of potentiometer I, the positive pole beingconnected to the left end of the winding. The wiper. I4 will thus have apositive potential with respect to wire 28 propora tional to +a, andthis potential is supplied by the wire 21 to the control circuit. Thesource I6 is also connected across the winding of potentiometer 2, thepositive pole being connected to the left end of the winding. The wiperl5 will thus have a positive potential with respect to the wire '23. Thepotential drop across the whole winding of potentiometer 2 is madeproportional to 180 degrees, thus the voltage with respect to wire28selected by the wiper I5 is proportional to +(1805). This voltage issupplied by wire 29 to the left end of the winding of potentiometer 4.The source I! is connected across the winding of potentiometer 4, thepositive pole being connected to the left end of the winding. Thevoltage selected by the wiper 30 is thus negative with respect to wire29 and is approximately proportional to 'y. The potential of the wire 3|with respect to the wire 28 will thus be proportional to +(l80 3)y, butthis potential on the wire 3| opposes, in the control circuit 24, thepotential of the wire 21 and is thus eflectively reversed in polarity to(180-B) The sum of the voltages supplied to the control circuit 24 willthus be The control circuit 24 energizes the appropriate clutch 25 or 26to cause the shaft 23 to rotate, movin the wiper 30 and changing thevoltage representing the angle until the difference voltage ae=0, whenthe angular position of the wiper '30 and dial 4|, will represent theangle 7. that is,

the angle ATB, Fig. 1.

The potentiometer 3 has a winding varying in resistance per unit lengthas a sinusoidal function from to 180 degrees. The positive pole of asource of voltage 32 is connected to the midpoint of the winding of thepotentiometer 3 and the-negative pole is connected to both ends of thewinding. The voltage of the source 32 represents, to a scale of voltsper unit length, the

distance m between the observation points A and B. The wiper 33 is movedwith the wiper l by suitable linkage or gearing. The potentialdifierence between the wires 34, 35 will thus be proportional to +m sin)8.

The winding of the potentiometer 6- has a constant resistance per unitlength. The positive pole of a source of voltage 36 is connected to oneend of the windin of potentiometer '6 and to 4 36 is connected by wire31 to both the ends of the winding.

The voltage selected by the wiper 38 may be designated p. The wiper 39of the potentiometer 5 is driven bythe shaft 23, either directly orthrough suitable gearing, through the angle 7, Then the voltage selectedby the wiper 39 will be proportional to p sin 'y.

m -L. sin 7 sin 6 of sines thus m sin l3=p sin 'y and m sin ,8p sin :0.The servo-motor 4| is actuated by the difference voltage 662 to move thewiper 38 until the difference voltage is reduced to zero, thus makingthe potential difierence between the wire 31 and wiper 38 proportionalto p, in the same scale of volts per unit length as used for the baseline m, which may be indicated on a meter M.

The system shown in Fig. 4 is essentially the same as the system shownin Fig. 3 except that only one source of voltage 59 is required for thecomputations. The corresponding potentiometers and servo-motors in Figs.3 and 4 have similar reference characters.

The voltages selected by the wipers of the potentiometers I, 2 and 4are, in this case, all in parallel and of the same polarity with respectto the common return 5|, which may conveniently be grounded. The anglesa. and 'y are measured clockwise from the lower terminals of thepotentiometers l and 4. The angle -B is also measured clockwise from thelower terminal of the potentiometer 2, thus the angle 6 is measuredcounter-clockwise from the upper terminal of the potentiometer 2. It isthus necessary to reverse the polarity of the voltage from thepotentiometer 2 from a voltage representing +180-,8 to a voltagerepresentin 180+B. The polarity may be reversed by any suitable means,such as a thermionic repeater having an odd number of stages. A suitablerepeater for this purpose is disclosed in United States Patent2,401,779, patented June 11, 1946 by K. D. Swartzel, Jr., assigned totheassignee of the present application and shown in Fig. 5.

The repeater shown in Fig. 5, from one point of View, may be consideredas a low frequency amplifier having an odd number of stages, and usingsufficient reverse feedback to make the overall voltage gain equal tounity. The amplifier then becomes a repeater which reverses the polarityof the applied voltage, without changing the magnitude or wave shape.

The repeater shown in Fig. 5 has another valuable property. When aconductive load is connected across the output circuit, current can flowfrom battery 60, through resistor 6|, the connected load and wire 62back to battery. A second current can also flow from battery throughwire 62, the connected load, anode to cathode of vacuum tube 63 to anegative tap on the battery 60. By adjustment of the negative tap, thesecurrents may be made equal and. as these currents fiow in oppositedirections, no voltage drop will be produced across the load. Theapplication of a voltage through one of the input resistors, such 64,will produce a voltage on the control electrode of the vacuum tube 63which will upset this balance and produce a voltage across the loadcircuit equal to the applied voltage. A number of voltages may beapplied in parallel through the input resistors and a voltage will beproduced across the load circuit which is the sum of the appliedvoltages reversed in polarity.

The voltage selected by the wiper of potentiometer 2 is proportional to+180,B, and this voltage is reversed in polarity by the repeater 52 tobe proportional to l80+l3. The voltage se looted by the wiper of thepotentiometer l is proportional to +a, and the voltage selected by thewiper of potentiometer 4 represents All of these voltages are suppliedto the repeater 54 of the type shown in Fig. 5. The output circuit ofthis repeater will develop a voltage of the form +180-a-l3'y. Thisvoltage is supplied to the control circuit 24 of the servo motor l8, andactuates the servo-motor to rotate the wiper of potentiometer 4, varyingthe voltage selected by the wiper of potentiometer 4 to make the appliedvoltage equal zero, thus moving the wipersdf the potentiometers 4 and 5a distance proportional to 'y.

The added potentiometer 53 selects a voltage proportional to the baseline distance or which is reversed in polarity by the repeater 55, andapplied to the mid-point of the winding of potentiometer 3. The wiper ofpotentiometer 3 is moved with the wiper of potentiometer 2 through adistance proportional to the angle 5, thus selecting a voltageproportional to m sin 13.

The wiper of the potentiometer 6 selects a voltage representing theslant distance p and applies this voltage to the mid-point of thewinding of potentiometer 5. The wiper of potentiometer 5 is moved by theservo-motor i8 through a distance proportional to the angle v andselects a 5 voltage representing sin 'y. The voltages selected by thewipers of the potentiometers 3 and 5 are added in the repeater 56 toproduce a voltage of the form +m sin [3p sin 7 which is applied to thecontrol circuit of the servo-motor 4|.

The servo-motor 4| rotates the wiper of potentiometer 6 until thisapplied voltage is reduced to zero, thus making the voltage, withrespect to wire 5|, selected by the wiper of potentiometer 6proportional to p.

.6 v of the voltages from said means to adjust said adjustable means tomake the sum of said voltages zero, whereby said mechanism is movedpro-' portionally to the angle at said object subtending said base line,third means connected to said source and adjustedto select a voltageproportional to said known distance, fourth means connected to saidthird means and adjusted pro-' portionally to the angle at said secondstation to select a voltage of one polarity proportional to the productof said distance multiplied by the sine of the angle at said secondstation, other adjustable means connected to said source, fifth meansconnected to said other adjustable means and moved by said firstmechanism to fraction- I ate the voltage from said other adjustablemeans proportionally to the sine of the angle at said object, a secondmechanism connected to said fourth and fifth means and controlled by thesum of the voltages from said means to adjust said other adjustablemeans to make the sum of said voltages zero. whereby said secondmechanism is moved proportionally to the distance from said firststation to said object, and the voltage 1 from said other adjustablemeans is made proportional to said distance.

2. Apparatus for indicating the length of one side of a triangle whichcomprises, a source of a. first voltage of one polarity adjusted to beproportional in amplitude tov the measured length of another side. ofsaid triangle, an adjustable re sistor having a winding varying inresistance with a sinusoidal function connected to said source andadjusted to modify the amplitude of the voltage from-said sourceproportionally to the sine of an angle adjacent to said other side, asource of a second voltage of opposite polarity, motor driven meansconnected to said source for modifying the amplitude of said secondvoltage, a second adjustable resistor having a winding varying inresistance with a sinusoidal function connected to said means andadjusted to T modified amplitude of said second voltage,- and firststation between said base line and the line to said object, second meansconnected to said source and controlled by observations of said objectto produce a second voltage of opposite polarity proportional to thesupplement of the angle at said second station between said base lineand the line to said object, adjustable means connected to said sourceto fractionate the voltage from said source, a first mechanism connectedto all said means and controlled by the sum said indication, are madeproportional to said one side of said triangle.

CLARENCE A. LOVELL.

I DAVID B. PARKINSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 444,217 Fiske Jan. 6, 18911,154,252 Kennedy Sept. 21, 1915 1,368,224 Meitner Feb. 8, 19212,087,667 Hedin July 20, 1937 2,134,901 Wey Nov. 1, 1938 FOREIGN PATENTSNumber Country Date 4 218,548 Great Britain July 10, 1924

